This invention relates to vehicle safety devices, and more particularly to a collision avoidance device which can be mounted as a single unitary housing at approximately eye level on the rear of a leading vehicle so as to provide to the driver of a trailing vehicle an earlier visual indication and recognition of the safety "space cushion" distance between the vehicles.
A major cause of vehicle accidents today involves front-to-rear collisions. Leaving insufficient room between vehicles is the cause of one of the most costly and involved types of traffic accidents, the rear end collision. Rough estimates conservatively indicate that it accounts for more than one-third of all traffic mishaps, and one-half of the resulting injuries. In New York State it accounts for 40% of all vehicle accidents. Driving too close to a leading vehicle is the most basic driving error. Tailgating produces the deadliest damage, ranking as the number one cause of auto accidents and injuries on the highway.
Not only do such accidents result in loss of life and injuries which produces human suffering to persons and their families, but such accidents also produce a great cost in automobile repairs. Such rising repair costs and claim settlements are reflected into the increased fees that the insurance buying public must pay.
Nevertheless, rear end collisions are probably the easiest accidents to prevent. Generally, such collisions are the direct result of drivers trailing so closely that they cannot stop in time. When the forward vehicle provides a sudden stop, or even on occasion a gradual stop, the driver of the trailing vehicle fails to appreciate that stopping of his car involves a considerable number of factors.
In stopping a car, care must be paid to the reflexes of the individual driver. This, of course, varies with the type of driver, his age, his visual acuity, as well as the attention and alertness he is paying to the particular situation. It also depends upon other factors including the car speed, the road surface and slope, weather, tires, brakes, and even car weight. It varies between day time and night time driving, the amount of ambient light available, and numerous other factors, many of which may not even be considered by the average driver.
Because of the numerous factors involved it is almost impossible to specify an exact amount of distance required between cars at all times. Nevertheless, various safety organizations have provided recommendations based upon various average factors. For example, one safety organization recommends one car length for each 10 miles per hour of speed of the trailing vehicle. Another safety organization suggests a two second rule applied by selecting a fixed object on the road and counting for a time period of two seconds beginning as a leading vehicle passes the fixed object to indicate that you have approximately two seconds before the trailing vehicle reaches that object. Other organizations have provided yet further, and frequently more complex suggested measuring systems.
The basic problem with all of the suggestions is that it requires detraction of the driver from the actual driving situation. The driver must spend so much of his awareness in determining the distance between his vehicle and the leading vehicle, that he may fail to devote his complete attention to the actual driving situation and may be distracted from an emergency stopping condition. It would therefore be superior to provide an indication of the safe trailing distance by focusing the attention of the driver of the trailing vehicle onto a visually centralized location on the leading vehicle. By providing at this central location the information concerning proper spacing distance required you can thereby avoid any distraction of the driver of the trailing vehicle from focusing on the driving scene and the leading vehicle.
One device which provides such visual indication of suitable distance between the vehicles is described in U.S. Pat. No. 3,868,629, entitled "Visual Collision Avoidance Warning Device," issued Feb. 25, 1975 to the inventor of the present application. In this invention, there is provided a warning device on the back of a leading vehicle which includes a plurality of pairs of adjacent lights. The size of both of the lights of a single pair are identical. However each pair of lights increases in size from the previous pairs. The lights of a particular pair are associated with a particular speed. At a suitable distance between the vehicles, the lights of a pair will merge. Accordingly, by focusing onto a particular pair of lights corresponding to a particular average speed, the driver of a trailing vehicle can determine if he has adequate distance behind the leading vehicle. If he sees that pair of lights as two separate and distinct lights, he is too close. On the other hand, if the lights have merged, then he has adequate spacing for the speed.
In U.S. Pat. No. 3,950,098 issued Apr. 13, 1976 to the inventor of the present application, entitled "Safe Distance Visual Warning Device", there is provided another distance warning device. In that patent, there is provided a series of geometric areas of progressively increasing size. Each area is assigned to a specific speed. At the particular speed, if that particular geometric area can be distinctly seen, then the distance is inadequate for the speed. For adequate distances at that speed, that particular geometric area will merge with previous geometric areas assigned to lower speed.
While the aforementioned devices can improve the awareness of the driver of the trailing vehicle, further improvement in stimulating the driver's visual perception and mental awareness can bring about even further improved results. For example, providing an improvement of awareness or reaction time of even 1/10th of a second not previously available gives an additional three feet of stopping distance at 20 miles per hour, six feet at 40 miles per hour, and as much as nine feet at 60 miles per hour. These extra feet can be the difference between a safe stop and a rear end collision. Accordingly, even 10ths of seconds of improvement in awareness or reaction time is of considerable significance. It should be noted that these computations are made in connection with vehicles in motion.
More recently, there has been considerable private and governmental testing of a single high mount brake light to be provided centrally on the rear of a leading vehicle. This is now becoming mandatory on all new vehicles. Through various tests, it has been found that such central high mounted brake light provides greater and improved recognition factors to the driver of the trailing vehicle and improves his earlier reaction time by about 1/10th of a second to an emergency condition where the brake light has been applied by the leading vehicle.
It is therefore of considerable importance, to integrate various of the visual cues as safety measures provided on the rear of a leading vehicle in order to minimize and/or to avoid rear end collisions. These include the use of the high mount single brake light centered at eye level, as well as the use of the safe distance single light on the rear of a vehicle to provide indications of safer "space cushion" stopping distance. The use of the safe distance signal light also provides environmental cues to the driver to signal the behavior that is needed and thereby help modify the human behavior with regard to tail-gating as well as other driving situations.